The intracellular domain of FcαRI is important for cytokine-induced IgA binding.

(A) Schematic diagrams of FcαRI and different FcαR-deletion mutants are shown. (B) The expression of the receptors was analyzed by flow cytometry. (C) Ba/F3 cells expressing FcαRI mutants were used for IgA-rosette assays. Cells were cytokine starved and subsequently stimulated for 15 minutes with either buffer (■) or IL-3 (░). IgA binding to the cells was measured by the formation of rosettes between cells and IgA-coated beads. Results are expressed as rosette index and as means ± SE (n = 3).